Vinyl chloride copolymers



United States Patent The present invention relates to novel vinyl chloride interpolymers and to methods for preparing same.

Vinyl chloride homopolymers are widely employed as a surface coating resin, as a wire insulation resin, and for diverse other purposes. A relatively recent develop ment in the art has been the employment of vinyl chloride polymer insulated wires as underground electrical cables. The insulation on such underground cables must be able to withstand severe physical punishment and for maximum utility requires vinyl chloride polymers having physical properties superior to those of many of the pres- 1 ently commercially available vinyl chloride homopolymers. In particular, this development requires vinyl chloride polymers having a high tensile strength, a high 100% modulus and a high crush-resistance.

It is known that the physical properties of vinyl chloride homopolymers such as tensile strength, 100% modulus and crush-resistance can be improved by preparing the polymer under such conditions that higher molecular weights are obtained. To obtain suchhigher molecular weights it has heretofore been, necessary to lower the polymerization temperature or-to reduce the concentration of free radical generating polymerization initiator employed or both. Such modifications of the polymerization process increase the cost of preparing vinyl chloride homopolymers in that they lower the rate of polymerization and concomitantly the productive capacity of the equipment in which the polymer is prepared.

A method sometimes proposed for increasing the molecular weight of polymers is to incorporate a small quantity of a cross-linking monomer, i.e., a monomer containing two or more non-conjugated terminal ethylenic groups, in the monomer charge. This method has been used successfully with some polymer systems, but it is not generally applicable to the preparation of vinyl chloride polymers of high molecular weight. In particular, it is diificult to find cross-linking monomers which will interpolymerize with vinyl chloride at satisfactory rates. Moreover, where interpolymers can be formed, they tend to be quite heterogeneous in composition and in most cases the interpolymer contains a highly gelled fraction which is insoluble in most solvents for the vinyl chloride interpolymer. Such interpolymers, because of their heterogeneity and insoluble gel fraction, can not be employed in surface coating compositions.

It is an object of this invention to provide vinyl chloride polymers having improved physical properties.

Another object of this invention is to provide a process for preparing vinyl chloride polymers of improved physical properties, which process can be carried out in conventional polymerization equipment.

A further object of this invention is to provide a vinyl chloride polymerization process which, with no sacrifice in the rate of polymerization, yields vinyl chloride polymers of improved physical properties.

Other objects and advantages of this invention will be apparent from the following detailed description thereof.

It has been discovered that vinyl chloride polymers of improved physical properties, as compared with vinyl chloride homopolymers prepared under otherwise identical conditions, can be obtained by interpolymer-hing minute but critical quantities of an N-allyl substituted acrylamide with vinyl chloride. Such improved vinyl chloride interpolymers contain 0.003-0.30 weight percent of the N-allyl substituted acrylamide with the balance of the interpolymer being vinyl chloride. The vinyl chloride interpolymers of improved physical properties are obtained .at rates of polymerization which are fully equivalent to those obtained in the homopolymerization of vinyl chloride.

As noted earlier herein, it is known that the physical properties of vinyl chloride polymers such as tensile strength, modulus and crush-resistance are improved as the molecular weight of the vinyl chloride polymer is increased. This is true not only for vinyl chloride polymers per se, but also for formulated vinyl chloride polymer compositions containing plasticizers, pigments, fillers and other conventional polymer compounding ingredients. Since the precision of molecular weight determinations is much higher than the precision of determinations of tensile strength, 100% modulus and crush-resistance, the comparison of polymer properties in the subsequent examples is based primarily upon polymer molecular weights, such molecular weights being expressed in'terms of the specific viscosities of the polymers. All of the specific viscosities reported herein are determined on 0.4 weight percent solutions of the polymer in cyclohexanone at 25 i0.05 C. The precision of the reported values is i0.002. The formula employed for calculating specific viscosities is set forth below:

Solution viscosity-solvent viscosity Solvent viscosity The following examples are set forth to illustrate more clearly the principle and practice of this invention to those 'skilledin the art. All parts are by weight.

EXAMPLE I Part A A vinyl chloride homopolymer is prepared in a stirred autoclave employing the suspension polymerization system set forth below:

Specific viscosity= Component: Parts by weight Monomer 100 Water 1 Suspending agent 1 0.1 5 Lauroyl peroxide 0.25

Equimolar interpolymer of vinyl acetate and maleic anhydride The polymerization is carried out at 51 C. and is completed in about 16 hours. The vinyl chloride homopolymer has a specific viscosity of 0.51.

Part B An interpolymer consisting of 99.98 weight percent of vinyl chloride and 0.02 weight percent of N,N-diallyl acrylamide is prepared by the procedure of Part A aboveand has a specific viscosity of 0.60. In comparing specificvis'cosity value with the specific viscosity of the vinyl chloride homopolymer' prepared in Part "A above, it will be noted that, although the interpolymer A are both compounded into the wire coating formulationsetforth below:

Component: Parts by weight Resin 100 Di(2-ethylhexyl)phthalate 42 Secondary plasticizer 22 r 7.... a m. -alcinm carbonate. .7 15 Stabilizer 1 8 nubrieant l1 '1 Hydrocarbon type. V The tensile strength and 100% modulus of the two wire coating formulations are set =l'orth in Table I.

TABLE I r 7 Tennis 100% Polymer Strength, Modulus,

p.s.i. psi.

vin i Chloride N,N-'Diallyl Acrylamide Int/erplyIl1er 2,020 1;810 Vinyl Chloride Homopolymer... 2, 500 1, 700

EXAMPLES III-VII -Five vinyl chloride-N,N-dia ll yl acrylamide interpolymers containing varying quantities of N,N-diallyl acryl- ,4 where R and R are independently selected from the group consisfingof a hydrogen atom and -a methyl radical and R" is selected from the group consisting of a hydrogen atom, an allyl radical and a methallyl radical. Typical examples of allyl acrylamides fulfilling the above formula include N-allyl acrylamide, N-methallyl acrylamide, N,N-dialyl methacrylamide, and N,N-dimethallyl methacrylamide. These -allyl acrylarnides can be prepared by'classical'ch'emical methods and are commercially 'available. For diverse reasons, including cost and ease of polymerization, the vinyl chloride-N,N-diallyl acrylamide interpolymers are the preferred species of the invention.

The proportions of vinyl chloride and allyl acrylamide included in the interpolymers will depend upon the structure of the allyl acrylarnide. When R" in the above formula is an allyl radical or a methallyl radical the interpolymer will consist of 99.9599.99 7 and preferably 99.97-99.995 weightpercent of vinyl chloride and, correspondingly, 0.05-0.003and preferably 0.03-0.005 weight percent of the allyl acrylamide. When R" in the above formula is a hydrogen atom, the interpolymer will consist of 99.7099.99 and preferably 99.85-99.98 weight percent of vinyl chloride and, correspondingly, 0.30-0.01 and preferably 0.150.02 weight percent of the allyl acrylamide.

The intenpolymers of the invention are preferably prepared bythe well-known suspension polymerization process in which the monomers are dispersed as small droplets in waterand polymerized therein. Although a watersoluble 'interpolymer of vinyl acetate and maleic an- I :hydride has been employed as the suspending agent in the examples herein prm'ented, other known suspending agents such as gelatine, protective colloids, etc. may be employed desired. The polymerizations are carried out at temperatures in the range of 3070 C. in the presamide are prepared under identical polymerization conditions following the procedure of Example I, Part B. The composition of the interpolymers and the specific viscosities thereof are set-forth in Table II.

TABLE 11 Wt. Percent; Polymer N;N-Dia1lyl Specific Acrylamide in Viscosity Interpolymer Control-Vinyl Chloride Homopolymer 0 I. 0. 51 I 0.003 I 0. 52 0.005 0.53 0.010 0. 55 0.020 r 0. 60 0.025 0.63

seen Erom Ttheabovetable, each of the interpoly rners containing MN-diallyl acrylatnide has a higher specific viscosity than the control vinyl chloride homo polymer. Each of the N,N-d-iallyl acrylamide containing .interpolymers also has a higher tensile strength and 100% inodiilus "than the control vinyl chloride homopolymer. In addition, each of the interpoly'mers is free of gels and "isconipletely soluble in suchsolvents as cyclohexanone and nitrobe'nzene. Accordingly, the inti'eijpolyiners are 'well suited for use in paints and other surface coating compositions.

The inter olymers of this invention are binary interpoly'mers consisting of vinyl chloride and an N-allyl subis'tituted acrylarnide, which for the sake of brevity will "sometimes be referredto simply as [the allyl acryl'amide. The allyl acrylamides which can be employed in the practice of this invention conform to the formula: n on n" enFe-li-N-enr =en,

ence of free radical generating polymerization initiators such as lau'royl peroxide, benzoyl peroxide, etc.

The interpolymers of this invention have higher molecular weights and better physical properties than corresponding vinyl chloride 'homopolymers prepared under identical polymerization conditions. Thus, the process of this invention makes possible the attainment of a superior product at no increase in cost. Alternatively, interpolymers of this invention having equivalent physical properties to vinyl chloride homopolymers can be prepared lat higher polymerization temperatures. Polymer- -izing "the interpolymers at higher temperatures increases the rate of polymerization and raises the productive capacity ot the polymerization vessel in which the reaction is carried out. This, "the interpolymers of this invention make possible the attainment of a higher productive capacity per miter-capital investment. In general, the productive "capacity of a polymerization vessel for the interpolymers of this invention is approximately 30% higherthan theproduc'ti'on capacity of the same vessel for a vinyl chloride homopolyer, both of said polymers being polymerized under conditions which give identical molecular weights.

The interpolymers of this invention may be used interchangeably with vinyl-chloride homopolymers in virtually all industrial applications. The interpolymers are parliciilarly suitable fornse in the insulation of electric wire and particularly for electric wire that is to be employed as :undergr'ound cable.

The'ab'ove descriptions and particularly the examples are set forth by way .of illustration only. Many other variations and modifications thereof will be obvious to thoseskilled in theart and can be made without departing Irom the spirit and scope of the invention herein disclosed.

What is claimed is:

l. Aresinous interpolymer "of a binary mixture of monomers consisting of vinyl chloride and an allyl acrylamide monomer of the formula:

where R and R are independently selected from the group consisting of a hydrogen atom and a methyl radical and R" is selected from the group consisting of a hydrogen atom, an allyl radical and a methallyl radical; said monomer mixture consisting of 99.70-99.99 weight percent of vinyl chloride and, correspondingly, 0.30-0.01 weight percent of the allyl acrylamide when R" in the above formula is a hydrogen atom; said monomer mixture consisting of 99.95-99.997 weight percent of vinyl chloride, and, correspondingly, 0.05-0.003 weight percent of the allyl acrylamide when R in the above formula is a substitutent other than a hydrogen atom.

2. A resinous interpolymer of a binary mixture of monomers consisting of vinyl chloride and an allyl acrylamide monomer of the formula:

where R and R are independently selected from the group consisting of a hydrogen atom and a methyl radical and R" is selected from the group consisting of a hydrogen atom, an allyl radical and a methallyl radical; said monomer mixture consisting of 9985-9998 weight percent of vinyl chloride and, correspondingly, 0.15-0.02 weight percent of the allyl acrylamide when R in the above formula is a hydrogen atom; said monomer mixture consisting of 99.97-99.995 weight percent of vinyl chloride and, correspondingly, 0.03-0.005 weight percent of the allyl acrylamide when R" in the above formula is a substituent other than a hydrogen atom.

3. A resinous interpolymer of monomers consisting of 9985-9998 weight percent of vinyl chloride and, correspondingly, 0.15-0.02 weight percent of N-allyl acrylamide.

4. A resinous interpolymer of monomers consisting of 99.97-99.995 weight percent of vinyl chloride and, correspondingly, 0.03-0.005 weight percent of N,N-dially1 acrylamide.

5. A resinous interpolymer of monomers consisting of 99.97-99.995 weight percent of vinyl chloride and, correspondingly, 0.03-0.005 weight percent of N,N-dimethyallyl acrylamide.

6. An insulated electric wire comprising an electrical conductor carrying an insulating coating of a resinous interpolymer of a binary mixture of monomers consisting of vinyl chloride and an allyl acrylamide monomer of the formula:

where R and R' are independently selected from the group consisting of a hydrogen atom and a methyl radical and R is selected from the group consisting of a hydrogen atom, an allyl radical and a methallyl radical; said monomer mixture consisting of 99.70-99.99 weight percent of vinyl chloride and, correspondingly, 0.30-0.01 weight percent of the allyl acrylamide when R" in the above formula is a hydrogen atom; said monomer mixture consisting of 99.95-99.997 weight percent of vinyl chloride and, correspondingly, 0.05-0.003 weight percent of the allyl acrylamide when R" in the above formula is a substituent other than a hydrogen atom.

7. A suspension polymerization process for preparing a resinous interpolymer of a monomer mixture consisting solely of vinyl chloride and an allyl acrylamide, which process comprises dispersing the monomers as droplets in an aqueous medium containing therein a suspending agent and polymerizing the monomers at a temperature of 30-70 C. in the presence of a free radical generating polymerization initiator; said allyl acrylamide conforming to the formula:

where R and R are independently selected from the group consisting of a hydrogen atom and a methyl radical and R" is selected from the group consisting of a hydrogen atom, an allyl radical and a methallyl radical; said monomer mixture consisting of 99.70-99.99 weight percent of vinyl chloride and, correspondingly, 0.30-0.01 weight percent of the allyl acrylamide when R" in the above vformula is a hydrogen atom; said monomer mixture consisting of 99.95-99.997 weight percent of vinyl chloride and, correspondingly, 0.05-0.003 weight percent of the allyl acrylamide when R" in the above formula is a substituent other than a hydrogen atom.

8. A suspension polymerization process for preparing a resinous interpolymer of a monomer mixture consisting solely of vinyl chloride and an allyl acrylamide, which process comprises dispersing the monomers as droplets in an aqueous medium containing therein a suspending agent and polymerizing the monomers at a temperature of 30-70 C. in the presence of a free radical generating polymerization initiator; said allyl acrylamide conforming to the formula:

where R and R are independently selected from the group consisting of a hydrogen atom and a methyl radical and R" is selected from the group consisting of a hydrogen atom, an allyl radical and a methallyl radical; said monomer mixture consisting of 99.85-99.98 weight percent of vinyl chloride and, correspondingly, 0.15-0.02 weight percent of the allyl acrylamide when R in the above formula is a hydrogen atom; said monomer mixture consisting of 99.97-99.995 weight percent of vinyl chloride and, correspondingly, 0.03-0.005 weight percent of the allyl acrylamide when R" in the above formula is a sub stituent other than a hydrogen atom.

References Cited in the file of this patent UNITED STATES PATENTS 2,580,277 Boyd et al. Dec. 25, 1951 2,771,457 Barnes et al. Nov. 20, 1956 2,773,063 Specht et al. Dec. 4, 1956 2,862,912 Ott Dec. 2, 1958 

1. A RESINOUS INTERPOLYMER OF A BINARY MIXTURE OF MONOMERS CONSISTING OF VINYL CHLORIDE AND AN ALLYL ACRYLAMIDE MONOMER OF THE FORMULA: 